About the disease
Johne’s disease is a chronic wasting disease caused by the bacterium Mycobacterium paratuberculosis. It lives in animal intestines, but can survive in the outside environment for many months.
M.paratuberculosis infection causes the intestinal wall to thicken and reduces the normal absorption of nutrients from grazing. An infected animal can eventually starve to death.
Clinical signs and symptoms of JD in cattle
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Animals are typically infected at birth however the disease is slow to develop, and clinical signs are often not seen until between 2 and 6 years of age in cattle.
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The numbers of infected cattle in a herd may start out low but the rate on infection is high and will not take long for there to be visibly sick and dying animals causing animal welfare issues as well as reduced enterprise production.
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The most common signs of JD in cattle are:
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Weight loss
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Chronic Diarrhoea (scouring)
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Decreased milk production
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Roughening of the coat and bottle jaw. Bottle jaw is a soft swelling under the jaw which is due to excessive protein loss.
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How does the disease spread?
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Infected older animals shed bacteria in their faeces to young calves. In the early stages of the disease this shedding may be minor and intermittent, whilst in later stages animals can become super shedders, shedding up to 10 million bacteria per gram of faeces.
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The disease can be triggered or worsened by stress, so in its early stages animals may appear Johne’s free until shedding is triggered, possibly only for a small period of time, by stress. For this reason, diagnoses of Johnes can be difficult.
Prevention
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A management framework to prevent Johnes Disease should consider the following:
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Developing and implementing a farm biosecurity plan
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Only purchasing animals with an animal health statement and introducing low risk stock onto your property
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Implementing grazing strategies to prevent the spread of of the bacteria
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Weaning early to limit infection
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Vaccinating
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